The very high degrees of purity required for the production of integrated circuits of very high density require limiting to the minimum the risks of contamination in the installations for the distribution of gas supplying these installations and products, at the source, with very high purity. In the distribution installation, there are essentially three sources of contamination resulting from problems of losses or retro-diffusion (principally for water vapor and oxygen), of out-gassing from the elements of the installation itself (essentially for water and hydrogen) and dead spaces. The first approach to limit these risks of contamination has consisted in using extremely carefully made conduits that have been subjected to particular internal treatments, essentially an electropolishing or a chemical treatment, and special active members such as bellows valves, diaphragm valves, valves comprising special arrangements, and assemblies without flanges. This special equipment is extremely troublesome, complicating the production of the installation, and certain elements of the special components, particularly the bellows, constitute additional traps for humidity and impurities.